Okay, here it is:

I have a slight erratic idle at normal operating temperature on my 98 LX 5spd with 50K miles. The tach will sit at ~ 750 rpm, and then blip down slightly (maybe 650?) before coming up again. Kind of annoying in and of itself, but as the revs fall, this causes either the hood or the hood latch to vibrate. This seems to be some kind of resonant frequency for the hood/latch. If the car is idling, and I push down on the hood, the noise goes away. So, ideally I'd like to figure out what's wrong with my idle, but solving the rattling by itself will work too! Thanks in advance.

 

Does your car idle irratically at cold starts, or just at normal starts? Because my car (56K miles) would do the same, I would hold the brake, and since I do not have a tach I can't say at what rpm, my car just wants to lurch forward little by little. But if I drop the tranny in neutral, it does not do that. I am not sure if our injection system is clogged, or dirty fuel filter, or something else.

As for the hood rattling, open the hood, and you should see at both corners, there are two rubber stumps. They are the ones the hood lands on when you shut it. The stumps are screws themselves, so if you turn them, you can either lower or raise the hood a little. I raised mine a little, and it stopped making the rattling noise.

 

ok i get that hood rattle too...but i only started noticing it in the winter season. when the car is nice and warm it doenst do it. Im gonna raise those rubber thingys soon

 

My hood was rattling just like yours, at standing idle. On the 1st gen, the hood bumpers aren't screwed in, just snapped in. I replaced both of those, plus the left side bumper at the midpoint of the fender (it was missing when I bought the car) - I still had the darn rattle. What ended up fixing it was adjusting the hood latch assembly. On mine, there's one bolt that you can loosen and it will let you move the latch up a little. Maybe that'll work on a 2nd gen too.